ExpandoObject.ContainsKey and ExpandoObject.Keys.Contains return different results

[loftyinclination]

I'm attempting to test whether an ExpandoObject contains a given key. The object is created, the key added, and then removed. Using the IDictionary.ContainsKey method returns false, but using IDictionary.Keys.Contains returns true.

This seems to be because the ExpandoObject.Remove method does not actually remove the key from the private _data field, but instead sets the value to ExpandoObject.Uninitialized. Then, the ExpandoObject.KeyCollection.Contains method does not check whether or data stored the ExpandoObject._data is Uninitialized, as ContainsKey does.

[loftyinclination]

To reproduce:

IDictionary< string, object > expando = new ExpandoObject();

var key = "key";

expando[ key ] = new object();
expando.Remove( key );

var containsKey = expando.ContainsKey( key ); // = false
var keysContains = expando.Keys.Contains( key ); // = true

Tagging subscribers to this area: @cston
See info in area-owners.md if you want to be subscribed.

[cston]

It looks like the same behavior exists in .NET Framework 4.8.

Also, expando.Keys.Count returns 0, even though expando.Keys.Contains(key) returns true.

[dotnet-policy-service]

Due to lack of recent activity, this issue has been marked as a candidate for backlog cleanup. It will be closed if no further activity occurs within 14 more days. Any new comment (by anyone, not necessarily the author) will undo this process.

This process is part of our issue cleanup automation.

[dotnet-policy-service]

This issue will now be closed since it had been marked no-recent-activity but received no further activity in the past 14 days. It is still possible to reopen or comment on the issue, but please note that the issue will be locked if it remains inactive for another 30 days.